text: From the perspective of bonding, carbodiimides are isoelectronic with carbon dioxide. Three principal resonance structures describe carbodiimides: 
  :RN=C=NR ↔ RN≡C-NR ↔ RN-C≡NR
  The N=C=N core is relatively linear and the C-N=C angles approach 120°. In the case of C(NCHPh), the central N=C=N angle is 170° and the C-N=C angles are within 1° of 126°. The C=N distances are short, nearly 120 pm, as is characteristic of double bonds. Carbodiimides are chiral, possessing C-symmetry and therefore axial chirality. However, due to the low energy barrier to the molecule rotating and thereby converting quickly between its isomers, the actual isolation of one optical isomer of a carbodiimide is extremely difficult. It has been demonstrated at least once, in the case of conformationally restricted cyclic carbodiimides; though there are other reports of one-handed axially chiral carbodiimides, their validity has since been called into question on experimental and computational grounds.
  The parent compound, methanediimine, (HN=C=NH), is a tautomer of cyanamide.